﻿<p>The element type <em>IfcSlabType</em> defines commonly shared
information for occurrences of slabs. The set of shared information
may include:</p>
<ul>
<li>common properties within shared property sets</li>
<li>common material information</li>
<li>common material layer definitions</li>
<li>common shape representations</li>
</ul>

<blockquote class="note">
NOTE&nbsp; It is illegal to share shape representations as representation maps for occurrences of <em>IfcSlabStandardCase</em>.
</blockquote>

<p>It is used to define a slab specification (i.e. the specific
product information, that is common to all occurrences of that
product type). Slab types may be exchanged without being already
assigned to occurrences.</p>

<blockquote class="note">
NOTE&nbsp; The product representations are defined as
representation maps (at the level of the supertype
<em>IfcTypeProduct</em>, which gets assigned by an element occurrence
instance through the <em>IfcShapeRepresentation.Item[1]</em> being an
<em>IfcMappedItem</em>.
</blockquote>

<p>The occurrences of the <em>IfcSlabType</em> within building models
are represented by instances of <em>IfcSlabStandardCase</em> if the
<em>IfcSlabType</em> has a single associated
<em>IfcMaterialLayerSet</em>; otherwise they are represented by
instances of <em>IfcSlab</em>, or <em>IfcSlabElementedCase</em>.</p>

<blockquote class="history">
HISTORY&nbsp; New entity in IFC2x2.
</blockquote>

<p class="spec-head">Informal Propositions:</p>
<ol>
<li>The material assignment, if provided using the
<em>IfcRelAssociatesMaterial</em> relationship, shall not reference
the <em>IfcMaterialLayerSetUsage</em>.</li>
</ol>